Partial wave analysis of the reaction gamma p -> p omega$ and the search for nucleon resonances

An event-based partial wave analysis (PWA) of the reaction gamma p -> p omega has been performed on a high-statistics dataset obtained using the CLAS at Jefferson Lab for center-of-mass energies from threshold up to 2.4 GeV. This analysis benefits from access to the world's first high precision spin density matrix element measurements, available to the event-based PWA through the decay distribution of omega-> pi+ pi - pi0. The data confirm the dominance of the t-channel pi0 exchange amplitude in the forward direction. The dominant resonance contributions are consistent with the previously identified states F[15](1680) and D[13](1700) near threshold, as well as the G[17](2190) at higher energies. Suggestive evidence for the presence of a J(P)=5/2(+) state around 2 GeV, a "missing" state, has also been found. Evidence for other states is inconclusive

A Review on processing and mechanical performance of natural fiber composites

Natural fiber composite material is one of the emerging field in material engineering. A lot of research is going on to find natural fibers and their potential for large number of application. There are many techniques through which we can extract natural fibers from parent plant. These extracted fibers has to be embedded into polymer matrix by different processing methods. Selection of processing method depend upon type of polymer matrix, type of natural fiber and desired mechanical properties. The method of natural fiber processing greatly affect the resulted properties of fabricated composite. Along processing methods there are different factors which are responsible for influencing mechanical properties of natural fiber composites. This review paper focus on different natural fiber processing techniques and mechanical performance of natural fiber composites

Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction

We present results on the electroexcitation of the low mass resonances Δ(1232)P<sub>33</sub>, N(1440)P<sub>11</sub>, N(1520)D<sub>13</sub>, and N(1535)S<sub>11</sub> in a wide range of Q<sup>2</sup>. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for π electroproduction off the proton. The data were analyzed using two conceptually different approaches—fixed-t dispersion relations and a unitary isobar model—allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the Δ(1232)P<sub>33</sub> show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q<sup>2</sup>⩽6 GeV<sup>2</sup>. For the Roper resonance, N(1440)P<sub>11</sub>, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark (3q) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S<sub>11</sub> allowed us to obtain the branching ratios of this state to the πN and ηN channels via comparison with the results extracted from η electroproduction. The extensive CLAS data also enabled the extraction of the γ*p→N(1520)D<sub>13</sub> and N(1535)S<sub>11</sub> longitudinal helicity amplitudes with good precision. For the N(1535)S<sub>11</sub>, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a 3q excitation. The transverse amplitudes for the N(1520)D<sub>13</sub> clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q<sup>2</sup>>1 GeV<sup>2</sup>, confirming a long-standing prediction of the constituent quark model